MANCHESTER - Donald Trump will be at St. Anselm's College today addressing the deadliest shooting in modern U.S. history in a campaign speech originally intended to attack the presumptive Democratic nominee, Hillary Clinton.

Trump will appear at the college's Institute of Public Politics at 2:30 p.m. A rally planned in Portsmouth and a fund-raiser scheduled for tonight in Rye have both been cancelled in response to this weekend's tragedy which killed 49 people inside the club and left more than 50 others wounded. Trump will retool his talk in New Hampshire to "further address this terrorist attack, immigration and national security,"

Trump asserted Monday there are thousands of people living in the United States "sick with hate" and capable of carrying out the sort of massacre that happened Sunday.

"We can't let people in. ... We have to be very, very strong," the presumptive Republican presidential nominee said in one of a host of broadcast interviews ahead of a speech he planned later Monday in New Hampshire.

"The problem is we have thousands of people right now in our country. You have people that were born in this country" who are susceptible to becoming "radicalized," the billionaire real estate mogul told Fox News Channel's "Fox & Friends. He claimed that there are Muslims living here who "know who they are" and said it was time to "turn them in."

The gunman, identified by police as Omar Mateen, a 29-year-old U.S. citizen from Fort Pierce, Florida, opened fire with an assault-style rifle inside a crowded gay nightclub in Orlando early Sunday, killing at least 49 people before dying in a gunfight with police. Another 53 people were hospitalized, most in critical condition.

Trump's longstanding proposal to temporarily ban foreign-born Muslims from entering the United States has triggered outrage from Democrats and Republicans alike, who see it unconstitutional, un-American and counterproductive. But it has helped him win over many primary voters who fear the rise of Islamic extremism and believe that "political correctness" — the fear of offending Muslims — is damaging national security.

Trump said Monday "there are people out there with worse intentions" than the perpetrator of the shootings in Orlando early Sunday. "They have to report these people," he said.

"This is a case of surveillance," he said on CNN. "You will find that many people that knew him (the Orlando shooter) felt that he was a whack job."

"You look at the people that have come to the country, and are here, and for that we need intelligence-gathering," he said. "We have to look at the mosques. The (Muslim) communities know the people that have the potential for blowup."

Trump also said in a phone-interview with NBC's "Today" show that he would not support a ban on the sale of assault-style rifles in the wake of the weekend massacre at a gay nightclub in Orlando, Florida.

He told the network "there are millions" of such weapons already in circulation and said he didn't think instituting a ban would help.

"Absolutely, I wouldn't" support such a prohibition, the real estate mogul said, "because people need protection."

He said a ban essentially would mean "the bad guys would have assault rifles and the people needing protection will be standing there with BB guns."